<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
</head>
<script>
	f1();
	console.log(c);
	console.log(b);
	console.log(a);
	function f1(){
		var a=b=c=9;//全局变量的使用和判断，为 未加var的为全局变量
		console.log(a);
	console.log(b);
	console.log(c);
	}
	</script>

<body>
</body>
</html>
